The present invention relates to a rear derailleur mechanism for a bicycle.
A multi-gear bicycle uses a rear derailleur mechanism to shift the chain from one sprocket to an adjacent sprocket so as to enable a rider to go faster or climb hills more easily. Gear selection is made via an inner cable housed in an outer cable both of which extend from a lever positioned on the bicycle near the rider's hands to the rear derailleur mechanism. A first end of the inner cable is secured to the gear lever, a second end of said cable passes through an adjuster nipple fixed to a lug on the derailleur mechanism and is clamped by a cable clamp means to a pivoting portion of the derailleur mechanism. The outer cable has a first end abutting a plate at the gear lever and a second end located within the adjuster nipple. Tension on the inner cable results in its stretching and the adjuster nipple is rotated counter-clockwise to take up the "slack" in the inner cable. However, this action results in misalignment between the derailleur and the sprockets. Thus, there has been a long and unfulfilled need for a rear derailleur mechanism for a bicycle which permits the tension of the inner cable to be adjusted without affecting the alignment between the rear derailleur and the sprockets of the bicycle.